You can determine which of the features in the WorkingSet of a layer are visualized, by configuring a feature filter on a FeatureLayer. A Feature filter is a function that accepts a LuciadRIA Feature, and returns true if the Feature must be visualized. To set the Feature filter, use the filter property on the FeatureLayer:

Program: Setting a filter on a layer. The filter ensures only cities with a population less than a certain threshold are shown on the map. (from samples/selection/main.js)
citiesLayer.filter = function(feature) {
  return feature.properties.TOT_POP <= value;
};

Installing a feature filter does not modify the working set of the feature layer. All the data will still be queried by the client from the server, and loaded into memory.

If you want to limit the amount of data that the client queries, you must reconfigure the queryProvider on the loadingStrategy of the FeatureLayer. This is illustrated in the Dealing with large feature data sets article.